U.S. patent application Ser. No. 506,803, filed June 22, 1983 for "Tranformerless Solid State Electronic Watthour Meter"--Miran Milkovic, inventor and assigned to the General Electric Company, discloses a satisfactory, transformerless solid state electronic KWH meter which employs a low value current sensing resistor together with a load voltage sensing resistor and novel differential amplifier circuit connection to derive required current indicating and voltage indicating input signals to the KWH meter. Because the KWH meter circuit does not require a separate current sensing transformer, it is susceptible to fabrication using solid state semiconductor integrated circuit fabrication techniques. As a result, the meter can be made at relatively low cost and is small and light weight so that it can be mounted on or adjacent to power conductors and/or their insulating support members with suitable easily installed mounting devices and procedures.
While the above-described solid state electronic watthour meter disclosed in the above-noted U.S. patent application Ser. No. 506,803 is satisfactory for many uses, because of its direct connection to the power conductors to be metered via current and voltage limiting impedances, the meter circuit does not provide electrical isolation between the power components being metered and the metering circuit itself. To overcome this problem the present invention was devised.